The present invention relates to a data transfer apparatus for transferring data between a sectored storage medium and a system bus.
According to a serial data transfer scheme, a buffer of large memory capacity is used for temporary storage of multi-sector data transferred between a disk and a system bus to absorb transfer speed differences between them due to asynchronous operation. One shortcoming of this serial data transfer scheme is that it is impossible to reinitiate data transfer to the disk before data transfer to the system bus has been completed, and vice versa. Therefore, the time taken to complete a data transfer in response to a given instruction is the total of the serial data transfer operations, resulting in a substantial amount of time for executing a data transfer operation. Furthermore, since the best performance of a serial data transfer system is determined by the memory capacity of the buffer, it is impossible for the serial data transfer scheme to attain a higher efficiency. A further disadvantage is that it requires complex circuitry.
In another prior art system where first-in-first-out memories are used to permit parallel transfer operations, no data is retained in the memories after data transfer is completed. Therefore, if an error is detected in the transferred data, there is no way of knowing where the error has occurred, making it difficult to diagnose circuitry.